Given an array **arr[]** consisting of **N** positive integers, the task is to check if it is possible to reduce the size of the array to **1** by repeatedly removing the smallest element from a pair having absolute difference of 2 or 0 between them. If it is not possible to reduce, then print **“-1”**. Otherwise, print the last remaining element in the array.

**Examples:**

Input:arr[] = {2, 4, 6, 8, 0, 8}Output:8Explanation:

arr[] = {2, 4, 6, 8, 0, 8}, Remove 0 from the pair (2, 0).

arr[] = {2, 4, 6, 8, 8}. Remove 2 from the pair (2, 4).

arr[] = {4, 6, 8, 8}, Remove 4 from the pair (4, 6).

arr[] = {6, 8, 8}. Remove 6 from the pair (6, 8).

arr[] = {8, 8}. Remove 8.

arr[] = {8}

Input:arr[] = {1, 7, 3, 3}Output:-1Explanation:

arr[] = {1, 7, 3, 3}. Remove 1 from the pair (1, 3).

arr[] = {7, 3, 3}. Remove 3 from the pair (3, 3).

arr[] = {7, 3}. No more removals possible.

**Approach:** Follow the steps below to solve the problem:

- Sort the given array in ascending order.
- Traverse the array starting from the smallest element and check if there exists any pair of the adjacent elements having absolute difference other than
**2**or**0**or not. - If found to be true, then print
**“-1”**. Otherwlse, print the largest element present in the array as that will be the only remaining array element after performing the given operations.

Below is the implementation of the above approach:

## C++

`// C++ program for the above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to find the last remaining` `// array element after repeatedly removing` `// the smallest from pairs having absolute` `// difference 2 or 0` `void` `findLastElement(` `int` `arr[], ` `int` `N)` `{` ` ` `// Sort the given array in` ` ` `// ascending order` ` ` `sort(arr, arr + N);` ` ` `int` `i = 0;` ` ` `// Traverse the array` ` ` `for` `(i = 1; i < N; i++) {` ` ` `// If difference between` ` ` `// adjacent elements is` ` ` `// not equal to 0 or 2` ` ` `if` `(arr[i] - arr[i - 1] != 0` ` ` `&& arr[i] - arr[i - 1] != 2) {` ` ` `cout << ` `"-1"` `<< endl;` ` ` `return` `;` ` ` `}` ` ` `}` ` ` `// If operations can be performed` ` ` `cout << arr[N - 1] << endl;` `}` `// Driver Code` `int` `main()` `{` ` ` `int` `arr[] = { 2, 4, 6, 8, 0, 8 };` ` ` `int` `N = ` `sizeof` `(arr) / ` `sizeof` `(arr[0]);` ` ` `findLastElement(arr, N);` ` ` `return` `0;` `}` |

## Java

`// Java program for the above approach` `import` `java.util.*;` `class` `GFG` `{` ` ` `// Function to find the last remaining` ` ` `// array element after repeatedly removing` ` ` `// the smallest from pairs having absolute` ` ` `// difference 2 or 0` ` ` `static` `void` `findLastElement(` `int` `arr[], ` `int` `N)` ` ` `{` ` ` `// Sort the given array in` ` ` `// ascending order` ` ` `Arrays.sort(arr);` ` ` `int` `i = ` `0` `;` ` ` `// Traverse the array` ` ` `for` `(i = ` `1` `; i < N; i++) {` ` ` `// If difference between` ` ` `// adjacent elements is` ` ` `// not equal to 0 or 2` ` ` `if` `(arr[i] - arr[i - ` `1` `] != ` `0` ` ` `&& arr[i] - arr[i - ` `1` `] != ` `2` `)` ` ` `{` ` ` `System.out.println(` `"-1"` `);` ` ` `return` `;` ` ` `}` ` ` `}` ` ` `// If operations can be performed` ` ` `System.out.println( arr[N - ` `1` `]);` ` ` `}` ` ` `// Driver Code` ` ` `public` `static` `void` `main(String[] args)` ` ` `{` ` ` `int` `arr[] = { ` `2` `, ` `4` `, ` `6` `, ` `8` `, ` `0` `, ` `8` `};` ` ` `int` `N = arr.length;` ` ` `findLastElement(arr, N);` ` ` `}` `}` `// This code is contributed by code_hunt.` |

## Python3

`# Python program for the above approach` `# Function to find the last remaining` `# array element after repeatedly removing` `# the smallest from pairs having absolute` `# difference 2 or 0` `def` `findLastElement(arr, N):` ` ` ` ` `# Sort the given array in` ` ` `# ascending order` ` ` `arr.sort();` ` ` `i ` `=` `0` `;` ` ` `# Traverse the array` ` ` `for` `i ` `in` `range` `(` `1` `, N):` ` ` `# If difference between` ` ` `# adjacent elements is` ` ` `# not equal to 0 or 2` ` ` `if` `(arr[i] ` `-` `arr[i ` `-` `1` `] !` `=` `0` `\` ` ` `and` `arr[i] ` `-` `arr[i ` `-` `1` `] !` `=` `2` `):` ` ` `print` `(` `"-1"` `);` ` ` `return` `;` ` ` `# If operations can be performed` ` ` `print` `(arr[N ` `-` `1` `]);` `# Driver Code` `if` `__name__ ` `=` `=` `'__main__'` `:` ` ` `arr ` `=` `[` `2` `, ` `4` `, ` `6` `, ` `8` `, ` `0` `, ` `8` `];` ` ` `N ` `=` `len` `(arr);` ` ` `findLastElement(arr, N);` `# This code is contributed by 29AjayKumar.` |

## C#

`// C# program for the above approach` `using` `System;` `public` `class` `GFG` `{` ` ` `// Function to find the last remaining` ` ` `// array element after repeatedly removing` ` ` `// the smallest from pairs having absolute` ` ` `// difference 2 or 0` ` ` `static` `void` `findLastElement(` `int` `[]arr, ` `int` `N)` ` ` `{` ` ` ` ` `// Sort the given array in` ` ` `// ascending order` ` ` `Array.Sort(arr);` ` ` `int` `i = 0;` ` ` `// Traverse the array` ` ` `for` `(i = 1; i < N; i++)` ` ` `{` ` ` `// If difference between` ` ` `// adjacent elements is` ` ` `// not equal to 0 or 2` ` ` `if` `(arr[i] - arr[i - 1] != 0` ` ` `&& arr[i] - arr[i - 1] != 2)` ` ` `{` ` ` `Console.WriteLine(` `"-1"` `);` ` ` `return` `;` ` ` `}` ` ` `}` ` ` `// If operations can be performed` ` ` `Console.WriteLine(arr[N - 1]);` ` ` `}` ` ` `// Driver Code` ` ` `public` `static` `void` `Main(String[] args)` ` ` `{` ` ` `int` `[]arr = { 2, 4, 6, 8, 0, 8 };` ` ` `int` `N = arr.Length;` ` ` `findLastElement(arr, N);` ` ` `}` `}` `// This code is contributed by 29AjayKumar` |

## Javascript

`<script>` `// JavaScript program for the above approach` `// Function to find the last remaining` `// array element after repeatedly removing` `// the smallest from pairs having absolute` `// difference 2 or 0` `function` `findLastElement(arr, N)` `{` ` ` `// Sort the given array in` ` ` `// ascending order` ` ` `arr.sort();` ` ` `let i = 0;` ` ` `// Traverse the array` ` ` `for` `(i = 1; i < N; i++)` ` ` `{` ` ` `// If difference between` ` ` `// adjacent elements is` ` ` `// not equal to 0 or 2` ` ` `if` `(arr[i] - arr[i - 1] != 0` ` ` `&& arr[i] - arr[i - 1] != 2)` ` ` `{` ` ` `document.write(` `"-1"` `+ ` `"<br>"` `);` ` ` `return` `;` ` ` `}` ` ` `}` ` ` `// If operations can be performed` ` ` `document.write(arr[N - 1] + ` `"<br>"` `);` `}` `// Driver Code` ` ` `let arr = [ 2, 4, 6, 8, 0, 8 ];` ` ` `let N = arr.length;` ` ` `findLastElement(arr, N);` `// This code is contributed by Surbhi Tyagi.` `</script>` |

**Output:**

8

**Time Complexity:** O(N*log N)**Auxiliary Space:** O(1)

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